Safari loads new pages very slowly with long delays

Recently, Safari became super slowly on my MacBook Pro M1 Max. When I enter the Url for a new page, Safari pauses for several seconds before loading the page. After the new page is loaded, new searchers within the page load quickly, e.g. going to google.com takes time but then googling something is quick whereas clicking on a new page from the search results is slow again.

The issue is unique to Safari, e.g. Google Chrome loads all pages directly without delays. I have done the following unsuccessful attempts to remedy the issue:

Clear history and cache

I have cleared all history and cache in Safari and made several restarts of both Safari and the Mac.

Disabled extensions

I had four Safari web extensions which I have all disabled.

Update

I have updated my Mac and Safari to the most recent version of macOS Sequoia v.15.0. Note that I encountered the issue with Safari already before the update.

DNS server

By default the router's IPv4 and IPv6 addresses are displayed. I tried entering Google's addresses 8.8.8.8 and 8.8.4.4.

DNS prefetching

I have disabled DNS prefetching using

defaults write com.apple.safari WebKitDNSPrefetchingEnabled -boolean false

Disabling IPv6

I configured IPv6 to link-local only.

Importantly, the issue occurs only on my Mac, not on my iPhone and iPad. It seems also limited to my home WiFi, i.e. when I connected via hotspot to my mobile network, Safari performed normally like Google Chrome. It thus seems that the issue relates to router settings specific to my Mac. However, I have no idea where to start to resolve this issue, so any help is greatly appreciated.